Polyols represented by polyester polyol and polyether polyol produce polyurethane resins by reaction with isocyanate. Polyols constitute the soft segment portions in polyurethane resins, and largely contribute to physical properties of the polyurethane resins such as mechanical properties and durability. Since polyester polyol gives better physical properties to polyurethane resins in terms of mechanical strength and weatherability than other polyols, polyester polyol is widely used for polyurethane resins to be used as materials for synthetic/artificial leathers, plastic foams for shoe soles, thermoplastic resins, paints, adhesives, and the like.
Moreover, in recent years, global environmental issues have been attracting attention, and providing of materials that are conscious of the global environment is demanded. Also for polyurethane resins, use of materials derived from biomass resources such as plants instead of petroleum-derived materials is becoming popular.
In terms of biomass resources from which polyester polyols are derived, there are, for example, cases where biomass-derived succinic acid or castor-oil-derived sebacic acid is used as a material dicarboxylic acid, and cases where 1,3-propanediol obtained by a fermentation method or 1,10-decanediol derived from castor oil is used as a material diol. (Patent Documents 1, 2, 3, and 4)
On the other hand, unlike materials prepared from petroleum, most of the materials derived from biomass resources require a high-level purification process for increasing their purity since they contain a large amount of impurities. This often prevents their wide application as materials. The same applies to materials of polyester polyol. Materials which can be easily obtained without high-level purification and which give favorable physical properties to polyurethane resins are demanded.